Pneumatic-electric converter for dental instruments

ABSTRACT

A dental device having at least one pneumatically operable handpiece, the rotational speed of which can be influenced by a control element designed as a foot-operated switch, and a further handpiece, which can be driven by means of an electric drive, and the compressed air present at the pneumatic handpiece influences the control of the electric drive. A graduated filter is mounted on a pneumatically actuated hollow body and the graduated filter has regions thereon which can be sensed by a light barrier generating an electric signal in dependence on the properties of the regions.

BACKGROUND OF THE INVENTION

The invention relates to a dental device having at least oneelectrically operable handpiece, the rotational speed of which can beinfluenced by a control element designed as a pneumatic foot-operatedcontroller, the compressed air present at the output of the pneumaticcontrol element influencing the control of the electric drive.

German published patent application DE 24 17 890 discloses a dentaldevice in which at least one dental handpiece is connected to acompressed-air motor drive fed from a compressed-air source via acompressed-air line. The rotational speed can be changed by means of acontrol valve, controlling the compressed air, via a pneumatic controldevice, preferably designed in the form of a foot-operated switch. Whenusing a further handpiece with an electric motor drive, which can beswitched on and off via an electrical switching element and therotational speed of which can be controlled by means of an electriccontrol element, pressure converters are installed which control thecompressed air controlled by the control valve for the compressed-airmotor drive in such a way that an electric control element of theelectric motor drive is influenced. The rotational speed is varied atthe electric motor drive via an electric control element taking the formof a sliding contact.

It has be found that, in the case of pneumatic dental appliances whichcan be influenced in rotational speed by means of foot-operated control,the displacement to be completed at the foot-operated switch to bringabout a corresponding change in rotational speed at the dental handpieceis greater at low pressures. However, this only relates to pneumaticallyoperable dental handpieces. At greater pressures, a small change indisplacement at the foot-operated switch is already sufficient to bringabout a change in the rotational speed at the dental handpiece to bepneumatically operated. The subjective perception of the dentist onwhich this response is based can only be approximated by a non-linearcharacteristic, which is therefore also desirable for electricallyoperable handpieces.

To arrive at a characteristic with such a profile, which cannot bereadily realized for example with pressure transducers available forpurchase, electronic components (microprocessors, non-linear analogcircuits) would therefore have to be used to convert the signal. Thedentist would like to operate the electrically operable handpieceslikewise with the pneumatic foot-operated control, so that it must beensured that the rotational speed behavior of the electrically operablehandpieces corresponds to the pneumatically operable handpieces, so thatthe dentist can ideally operate both handpieces by means of hisaccustomed way of operating the foot-operated control, irrespective ofwhether a pneumatically operable handpiece or an electrically operablehandpiece is concerned.

SUMMARY OF THE INVENTION

The invention is based on the object of converting the signal of apneumatically actuated foot-operated control in such a way that theelectrically operable handpieces behave in a way proportional to apneumatically driven handpiece.

This object is achieved according to the invention by providing that adental device with at least one electrically operable handpiece, forwhich it is intended that the rotational speed can be influenced by afoot-operated controller and for which the compressed air downstream ofthe control element influences the control of the electric drive, isequipped with a graduated filter which is held on a pneumaticallyactuated hollow body, the graduated filter having formed on it regionswhich can be sensed by a light barrier generating an electric signal independence on the properties of the regions.

With the solution according to the invention, operation both of apneumatically drivable handpiece and of an electrically drivablehandpiece using a foot-operated control shared by both can be broughtabout, both the response of the pneumatically drivable handpiece and theresponse of the electrically drivable handpiece being made, by changesin the displacement at the foot-operated switch, to simulate thesubjective perception of the dentist approximated best by a non-linearcharacteristic. Small changes in current intensity, and consequentlysmall changes in rotational speed, at the electrically drivablehandpiece can be realized, in the case of low pressures and greatdisplacements at the foot-operated switch, by means of a p/I analogtransducer.

In an advantageous way, the graduated filter is designed as atransmission disk. This disk, divided into sectors of different surfacefinishes, may for example have been provided with a different degree ofblackening in each of its three or more sectors. As a result, differentoptical densities, lying between 0 and 4, can be realized. The degreesof blackening can be brought about for example by using a laser to workon the transmission disk serving as the graduated filter.

In a further refinement of the idea on which the invention is based, thepneumatically actuable hollow body is designed as a hollow spring, tothe spindle of which the transmission disk can be fastened. Thepneumatically actuable hollow body is part of a p/I analog transducer,the pressure chamber of which may have a connection to the hollow body,which may be designed as a hollow spring. The flexible hollow springmakes it possible to produce a deflection of the graduated filter aboutits spindle corresponding to the pressure in the p/I transducer. Thisdeflecting movement of the graduated filter is sensed by a lightbarrier, which encloses the edge, and consequently the sectors providedwith different surface finishes, of the graduated filter. Depending onthe deflection of the graduated filter about its spindle, the lightbarrier detects a certain sector region, so that an electric signalcorresponding to this sector region can be generated by the lightbarrier.

A likewise disclosed method of controlling the rotational speeds, on theone hand of an electrically drivable dental handpiece and on the otherhand of a pneumatically drivable dental handpiece, which can both beheld on a dental appliance and can be regulated in their rotationalspeed via a shared foot-operated control, comprises the following methodsteps:

applying the driving-air pressure to the input of the p/I analogtransducer,

deflecting a graduated filter by deforming a

sensing the deflection of the graduated filter by a light barrier whichis assigned to the latter and generates an electric signal, and

determining the current intensity [1] of the current [I]/pressure [p]characteristic.

By means of the method disclosed according to the invention, theelectric drive of the electrically operable handpiece can be controlledvia the foot-operated control with a response which corresponds to thatof the pneumatically drivable handpiece which can likewise be activatedvia the foot-operated control.

In the range of driving-air pressures of 0 to 1 bar, the currentintensity which can be preset at the electric drive increasesproportionately more weakly than in the case of driving-air pressures atthe p/I transducer which lie above a pressure of 1 bar.

BRIEF DESCRIPTION OF THE DRAWING

The invention will be explained more detail below with reference to adrawing, in which:

FIG. 1 is an exploded view of a p/I analog transducer according to theinvention;

FIG. 2 is a front view of the p/I transducer of FIG. 1;

FIG. 3 is a side view of the p/I transducer according to FIG. 2;

FIG. 4 is a graphic illustration of the desired progressive current[I)/pressure [p] characteristic; and

FIGS. 5a-c are graphic illustrations of the representation of severalcharacteristics; and

FIG. 6 is a schematic of a known dental appliance having basic features.

DETAILED DESCRIPTION OF THE INVENTION

The p/I analog transducer according to the invention shown in FIG. 1includes a held plate-shaped terminating part provided on a support part1 above fastening holes 2. The support part 1 of a pressure gage can befastened to the associated panel by means of bolts 4. In the supportpart 1 there are two holes, through which the bolts 4 are inserted inorder to fasten a part defining a pressure chamber 10 of a p/I analogtransducer to the support part 1. From the pressure chamber 10 of thep/I analog transducer there extends a pneumatically actuable hollow body7, which is designed in the embodiment of FIG. 1 as a hollow spring. Theflexible hollow spring 7 opens out into a pressure body 8, on the frontside of which a spindle 9 is fastened. The indicating disk 18 togetherwith the graduated filter 16 fastened thereto are held on the spindle 9.

Beneath the pressure chamber 10 of the p/I analog transducer, a hose 13is connected by means of a screwed inlet joint 12 to the pressurechamber 10, which is provided at its lower end with a nipple 14 togetherwith a sealing ring 15. The driving-air pressure present in thepneumatic pressure supply system is applied to the pressure chamber 10via the hose line 13.

The deflection of the graduated filter 16 fastened to the spindle 9 ofthe pneumatically actuable hollow body 7 is sensed by means of a lightbarrier 5, which embraces a clearance 6 between a first leg 5.1 and asecond leg 5.2. The graduated filter 16—a transmission disk in theexemplary embodiment indicated—is divided into a plurality of differentsectors 16.1, 16.2 and 16.3. Instead of the three sectors 16.1, 16.2 and16.3 represented here, a greater number of sectors may also be formed onthe periphery of the transmission disk 16. The sectors 16.1, 16.2 and16.3 may cover, for example, a range of 10° to 170° at the beginning ofthe transmission disk 16 and have an optical density increasing in thisrange from 0 to 4.

The pressure chamber 10 of the p/I analog transducer measures adriving-air pressure in the range between 0 and 4 bar and can be loadedwith 6 bar. The range of rotational speed at the dental handpiece forthis pressure range lies between 0 and 40,000 rpm.

The light barrier 5 encloses the edge region of the graduated filter 16with a first leg 5.1 and a second leg 5.2, between which the clearance 6lies. The beam emanating from the light barrier 5 may be, for example,an infrared beam of a wavelength of 935±5 nm. The infrared beam isattenuated displacement-dependently by the sector 16.1 or 16.2 or 16.3passing the clearance 6. The displacement-dependent attenuation can berealized, for example, by the sectors 16.1, 16.2 and 16.3 being providedwith different degrees of blackening, which can be achieved for exampleby using a laser to work on the transmission disk 16. The surface finishof the sectors 16.1, 16.2 and 16.3 can also be provided with differentroughnesses or the sectors may be made to have a different materialthickness, which could likewise be sensed by a light barrier 5.

The transmission disk 16 serving as the graduated filter is providedwith individual holes 17, into which pins 19 of an indicating disk 18engage. On the front side, the indicating disk 18 is provided with ascale 20.

The line 13 shown in FIG. 2, extending up to the pressure chamber 10from below, applies the blowing air pressure to the pressure chamber 10.This has the effect that the actuable hollow body 7 (see FIG. 1) lyingbehind the graduated filter 16 undergoes a deformation, which isdetectable from a turning of the transmission disk serving as thegraduated filter 16. The front view according to FIG. 2 reveals that thetransmission disk 16 can be designed with three sectors 16.1, 16.2 and16.3, which have a different degree of blackening in each case andtherefore differently attenuate an infrared beam penetrating it at thelight barrier 5. The light barrier 5 accordingly generates an electricsignal 21, which corresponds to the optical density of the detectedsectors 16.1, 16.2 or 16.3 and which can be used as a controlledvariable for the rotational speed of the electromotive drive of theelectrically drivable handpiece.

FIG. 3 shows that the component according to the invention is of quite aflat form and that the pressure chamber 10 for the driving-airconnection is largely enclosed by the support part 1 and the plate 3covering the latter. According to FIG. 3, the spindle 9, about which thegraduated filter 16 can be turned when the hollow body 7 is actuated bypressure, lies in line with the spindle of the indicating disk 18.

The profile of the current intensity (I), and consequently the profileof the rotational speed at the electrically operable dental handpiece,in dependence on the driving-air pressure (P) is explained on the basisof FIG. 4 with the subfigures 5 a to 5 c.

With the configuration of a p/I analog transducer described in FIGS. 1to 3, a characteristic profile which corresponds to the progressivecharacteristic profile designated in FIG. 4 by the reference numeral 27can be achieved. In the range of driving-air pressures which lie below 1bar, only small changes in the current intensity occur, while abovepressures of 1 bar the changes in current intensity, and consequentlythe changes in rotational speed at the electrically operable dentalhandpiece, are greater.

The calibration of the p/I analog transducer proposed according to theinvention can be performed according to FIGS. 5a-c for example by meansof a correction curve 26 stored in a micro-controller.

A linear pressure/displacement characteristic, as represented in FIG. 5aby the designation 22, can only be approximately reproduced by a linearcharacteristic 23 of the current intensity represented in FIG. 5b,plotted against the pressure (p). The ideal profile 24 of the currentintensity can be achieved, however, by a correction curve 26 which isrepresented in FIG. 5c and can be performed as part of a calibration ofthe p/I analog transducer to be carried out on a micro-controller. Withthe correction values 26 stored in the micro-controller, a correctedprofile 25 of the current intensity I over the pressure (p) can becalculated.

By the inclusion of the p/I analog transducer according to theinvention, the method of controlling the rotational speeds of apneumatically drivable handpiece and an electrically drivable handpiecevia a shared foot-operated control achieves a characteristic profilewhich increases the operating convenience of an electrically operablehandpiece by making its response to the control commands of thefoot-operated control approximate the response of the pneumaticallydrivable handpiece to the control commands by the foot-operated controlshared by the two handpieces.

FIG. 6 illustrates, as a schematic diagram, a prior art dental appliancehaving electrically drivable and pneumatically drivable handpiecesoperated by a foot-control through a microcontroller.

What is claimed is:
 1. A dental device with at least one electricallyoperable handpiece, the rotational speed of which can be influenced by acontrol element designed as a pneumatic foot-operated controller, thecompressed air present at the output of the pneumatic control elementinfluencing the control of the electric drive, wherein a graduatedfilter, mounted on a pneumatically actuated hollow body of the device,has regions which can be sensed by a light barrier generating anelectric signal in dependence on the properties of the regions.
 2. Thedental device as claimed in claim 1, wherein the graduated filtercomprises a transmission disk.
 3. The dental device as claimed in claim1, wherein properties of the regions comprise a surface finish thereof.4. The dental device as claimed in claim 1, wherein properties of theregions comprise a degree of blackening thereof.
 5. The dental device asclaimed in claim 4, wherein the degree of blackening progressescontinuously.
 6. The dental device as claimed in claim 1, wherein thepneumatically actuable hollow body comprises a hollow spring.
 7. Thedental device as claimed in claim 1, wherein the pneumatically actuablehollow body comprises part of a p/I analog transducer.
 8. The dentaldevice as claimed in claim 1, wherein the regions of the graduatedfilter are enclosed by the light barrier generating the electric signal.9. A method of controlling the rotational speeds of an electricallydrivable dental handpiece and of a pneumatically drivable dentalhandpiece, both of which are mounted on a dental appliance and can beregulated in rotational speed thereof via a shared foot-operatedcontrol, comprising the steps of: applying driving air pressure to aninput of a p/I analog transducer; deflecting a graduated filter bydeforming a hollow body which is part of the p/I analog transducer;sensing the deflection of the graduated filter by a light barrier whichis associated with the filter and which generates an electric signal;and determining current intensity of the p/I analog transducer inaccordance with a progressive current/pressure characteristic.
 10. Themethod as claimed in claim 9, having adjustable driving-air pressuresfrom 0 to 4, wherein in the range of driving-air pressures of 0 to 1bar, the current intensity which can be preset at the electric driveincreases proportionately more weakly than in the case of driving-airpressures above 1 bar.
 11. The method as claimed in claim 9, wherein thedetermination of the current intensity (I) of the p/I analog transduceris performed via a microcontroller, the correction curve being stored ina memory of the microcontroller.